1. Field of the Invention
The present invention relates to a tension panel and more particularly to a tension panel on which display sheets such as posters and banners can be displayed, being stretched tight.
2. Description of the Prior Art
There are various known methods for displaying a poster on a panel. One example is the method shown in FIG. 50, in which a poster is displayed on a panel, and is stretched under tension. According to this method, the upper and lower ends of a poster 400 are pinched by grips 401. These grips 401 are pulled in the directions (i.e., upward and downward directions) of the arrows by adjusting a plurality of screws connected to an aluminum panel 406, so that the poster 400 is stretched. Another example is shown in FIG. 51, in which the grips 401 are pulled upwards and downwards by means of a plurality of springs 405, each of which is secured to the panel 406 at one end thereof, whereby the poster 400 is stretched and displayed on the panel 406.
The panel 406 has the property of expansion with a rise in temperature, while the poster 400 has the property of expansion with a rise in humidity because it is made of paper, and temperature does not rise in proportion to humidity in the normal environment, so that the poster 400 tends to crease with time. More precisely, the poster 400 shown in FIG. 50 gets creases 402 in the areas retained by the grips 401 as shown in the figure, after a specified time has elapsed. It also gets curls 403 on its sides, which are not retained by the grips 401, and a vertically extending wavy line 404 at the center. The poster 400 shown in FIG. 51 gets less curls 403 but more wavy lines 404. Many creases 402 are created especially when humidity is high.
To prevent the formation of wavy lines 404, the sides of the poster 400 shown in FIG. 51 are further pinched at their middle parts by other grips 401a and pulled by springs 405a as shown in FIG. 52. With this method, the vertically extending wavy lines 404 are not formed, but obliquely extending wavy lines 404a are made, drawing a substantially diamond shape in the neighborhood of the four corners. Another improved method is such that the upper and lower ends of the poster 400 are retained at their respective lateral ends by means of grips 401b that are pulled upwards and downwards by the springs 405, as shown in FIG. 53. With this method, although the wavy lines 404 and curls 403 are not present, the creases 402 are inevitably formed in the areas retained by the grips 401, after the elapse of a specified time.
All of the above-described conventional methods disadvantageously take time in setting a poster and therefore there has been a strong demand for a quick displaying method.